What Exactly Is Terminal Services?

Can someone give me a general understanding of what Terminal Services is?

The reason I ask is this. I work for an ISP. We have a customer with four sites, all linked together through our network. They are currently using their applications in what i've been told is an incorrect manner (something about doing drive mapping across the WAN connection). I have heard that they are supposed to be using a Citrix server for this. I looked up Citrix and keep finding references to Terminal Services. But I cant find a clear explanation of exactly what it is. When i hear the word terminal I think of a text-based connection, like what you see when you telnet into a shell account or something. Is this what it looks like? How exactly does it work and why is it better than drive-mapping?

And in case your wondering, no i'm not the one in charge of fixing the problem. I'm just a new employee trying to gain a better understanding and our other network techs dont ever have the oppurtunity to fully explain whats going on here.

Terminal Services is a thin-client architecture that enables multiple users to run applications remotely on a "Terminal Server". All that is transferred between the client and server are essentially Display updates and User inputs (Keyboard/mouse). (Extensions to terminal services allow other things like sound, printer redirections, etc to be transmitted as well).

Citrix and Microsoft both have competing Terminal Services products, Metaframe and Windows Terminal Services, respectively. They also use different protocols called ICA (Citrix) and RDP(Microsoft). They operate on a broadly similar principle and either product can be used, although people usually have their own preference.

The reason that Terminal Services may be better than drive mapping is due to the amount of data transferred. Drive mapping implies that files are being remotely accessed over the WAN as they would in a LAN situation. In a 100Mbps LAN this may not be a problem, but even over a 2MB symmetrical link WAN link there may be issues. It is much better to have the applications running on a central Terminal server with only screen updates and user input being transferred over the WAN.

An excellent explanation as always from dalight.
It's worth mentioning though that considered like this, a terminal services solution soundls like network utopia and the cure for all your network ills. But be careful - the devil is often in the detail. I worked at one place where they ran an operation with about a hundred satellite offices and a main data centre. Each office had between two and twenty PCs in it and dealt with the public over the counter. They decided to rip out the PC-based thick-client application and installed a massive central Citrix Winframe server farm and put thin-client terminals out in the offices, justifying it all by being able to scale down the comms links to the satellite offices and thus saving money.
It worked great, really responsive screen operations, much faster than the old system - until somebody clicked 'print' (which they did at least once for each client served, over a hundred offices remember), at which point the entire print file had to be shoved along the downsized comms line out to the office to be printed. Result - big queues, grumbling customers, harassed staff and major egg-on-face for the executive that thought up the exercise

Good point Bishop!! I would have thought the cost savings should have been based more on reduction in support costs due to standardisation on thin clients and the centralisation of the application (server farms) rather than on downsizing the comms links, especially where heavy duty printing is involved. Typical Dilbert management scenario :roll: :roll:

Excellent information!

That pretty much told me everything I was needing to know to get a broad understanding of the matter.

Thank you as well for the real-word scenario described as that helps put it all in context.